Verification of Engine Torque and The Presence of Bearings
HIGHLIGHTS
Waveforms collected:
- Torque vs. Time
- Torque vs. Position
- Supply Pressure
- Back Pressure vs. Encoder
Analysis overview
- Breakaway torque
- Running torque
- Back pressure
- Supply pressure
Defects detectable:
- Tight pistons
- Missing main crankshaft bearing(s)
- Missing connecting rod bearings
- Debris in the crank journals
Potential defects
- Con rod defects (e.g., not torqued down properly)
- Bent cranks
A marine engine manufacturer buys engines from a major auto manufacturer, tears them down, changes components, and rebuilds them as 'marine ready'. A Sciemetric Test and Analysis System with InspeXion operating software was configured on a small engine assembly line to perform a short block test and check for defects in a high performance version of what was previously a normal 350 cubic inch block engine.
A handheld Atlas-Copco Nut Runner torque wrench tool was manually attached to the crank and used to turn the crankshaft for brief periods at a constant velocity. A separate encoder and torque sensor were used to measure breakaway and running torque against angle while air back pressure is also measured in the oil gallery as pressurized air is forced into the block. The supply line (with the supply pressure sensor inline) and back pressure sensors were attached to the engine with quick disconnect couplings, and a hole in the engine oil gallery was plugged to prevent leakage. The software button "Run Test" is pressed, and the operator is prompted to enter a serial number.
Once the serial number has been entered, the Sciemetric Test and Analysis System remotely starts the Atlas-Copco tool using a solid state relay (SSR) output. Breakaway torque, running torque and air pressure are measured and evaluated and a PASS/FAIL is indicated on the Sciemetric Test and Analysis System screen. Waveform data is saved for each engine as a PASS/FAIL with a filename that is 9 digits of the serial number entered by the user. A text log file is then updated with information from the test. The operator then disconnects the test apparatus from the engine and is ready for a new test. Additional plans to develop algorithms to identify which bearing is missing from the pressure waveforms are also scheduled.
Sciemetric worked with the engineers to provide a cost effective workable short block torque to turn test station with missing bearing air test capable of detecting all major failure modes they had identified.
